No 3rd party apps on the Apple iPhone, could it be a blessing?

I know this is old news but I have been thinking about Apple's stance on not allowing 3rd party software to be installed on the iPhone. Most people are not big fans of this policy because it limits the phone's options and I tend to agree. One of the big reasons I left Blackberry for Windows Mobile is the amount of cool 3rd party apps available for Windows Mobile platform. After thinking about Apple's policy it got me thinking.

Windows Mobile is a great platform and the base software is fairly stable. In reading forums, and from personal experience, I find that 90% of the time 3rd party apps are to blame for Windows Mobile's instability. Because it's easy to create apps for Windows Mobile I think a few applications don't go through a proper "beta" and are released a little buggy. Also 3rd party apps compatibility issues with each other can cause instability. I think Windows Mobile gets a bad rap on stability when it's not actually caused by Windows Mobile itself.

So, will not allowing 3rd party apps on the iPhone help keep it stable?